Help finding ADC with 3V analog input range

[ImperfectSeven]

Hi there, I need help finding a high speed ADC that meets the following specs:
at least 100MSPS
analog input range of at least 3V p-p
resolution is not a factor
preferably low power

So far the only one I have found is ADS5263 by TI
https://www.ti.com/lit/ds/symlink/ads5263.pdf

But with a price tag of 236.50 at 1k units I'm wondering if there is anything else.

Any help would be much appreciated

 

[AMSA84]

Have you tried to send an email to them in order to ask if they could send you a sample for academic purpose?

Regards.

 

[ImperfectSeven]

Well, its not exactly for academic purposes. I'm an intern and need an ADC that meets those specs to incorporate into a possible product.

 

[Mityan]

You better save your money buying ADC of 5 $ price and adjust input signal to 1 V p-p.
For example
https://www.analog.com/en/analog-to-digital-converters/ad-converters/ad9283/products/product.html

 

[keith1200rs]

You better save your money buying ADC of 5 $ price and adjust input signal to 1 V p-p.
For example
https://www.analog.com/en/analog-to-digital-converters/ad-converters/ad9283/products/product.html

Very true. I had a project recently with similar requirements. The cheapest overall solution involved a Linear Technology ADC which had a limited input voltage range AND had differential inputs. There just don't seem to be cheap, wide input range ADCs around.

Keith

 

[FvM]

There are well understandable reasons why a 100 MBPS ADC should use differential inputs. A number of recent ADC can be nevertheless used single ended with 0 - 3 V input range. A certain linearity reduction compared to fully differential input drive must be tolerated.

A fully differential amplifier gives you all options of voltage scaling, level shifting and single to differential conversion.

 

[ImperfectSeven]

There are well understandable reasons why a 100 MBPS ADC should use differential inputs.

Why is this? I'm rather new to ADCs and am learning as I go, I figured I would want a single ended input and even if I got a differential I could tie one input to ground and have the same thing as a single ended input.

 

[FvM]

Without differential inputs, the achievable signal-to-noise ration will be low, the higher the sampling rate and analog input bandwidth the worse.

You have to observe the common mode and differential voltage range specification of ADCs, tying one input to ground most likely doesn't work, better to a Vdd/2 reference voltage. But fully differential amplifiers cost only a fraction of a fast ADC, it's often the easier way.

 

[ImperfectSeven]

But won't using a differential with a Vdd/2 reference further limit my analog input range?

 

[FvM]

Most ADC with differential input have a bipolar voltage range, so biasing one the negative input to Vdd/2 can give e.g. 0..3V input range for a +/- 1.5 V differential input.

But you must check the individual ADC specifications. In addition, a resistive voltage divider can be used to scale the input voltage accordingly.

 

[ImperfectSeven]

so biasing one the negative input to Vdd/2 can give e.g. 0..3V input range for a +/- 1.5 V differential input.

I didn't quite follow that, can you maybe reword it?

 

[FvM]

The differential ADC inputs are usually bipolar.

 

[ImperfectSeven]

What about the LTC2229
It says it has 1Vp-p to 2Vp-p yet under the Maximum ratings it says that the Analog Input voltage can be from -0.3V to Vdd+0.3V which could be as much as -0.3V to 4.3V

 

[keith1200rs]

There is a difference between "Absolute Maximum" which means you won't blow it up and "working" ratings. The working range is +/-0.5V to +/-1V see page 3 of the datasheet.

Keith.

 

[FvM]

Absolute maximum ratings don't tell about correct function, but I know 1.8V ADC that are working corectly with input levels a few 100 mV beyond the supply rails. LTC2229 however has a +/-1V respectievely 2Vpp input range. That means, with An- at Vcm, Ain+ can swing from 0.5 to 2.5 V. To achieve a 0 to 3 V input range, the input must be divided down 1.5:1.

 

[ImperfectSeven]

There is a difference between "Absolute Maximum" which means you won't blow it up and "working" ratings.

Right, but if the absolute maximum is a 4Vp-p then surely I can get a 3Vp-p without harming the device?

Here is another ADC with even lower sampling rate but it has 3Vp-p (ADS807)
Plus, I like the over-range indicator. Since my signal is being amplified by a PSoC 3 I can use this to adjust the gains if I need to.

 

[keith1200rs]

Right, but if the absolute maximum is a 4Vp-p then surely I can get a 3Vp-p without harming the device?

It won't harm the device but you will hit full scale on the ADC once you reach +/-1V (or +/-0.5V depending on how you set up the ADC).

Keith.

 

[ImperfectSeven]

Ok so its basically saying you have a 1V window around Vref in which the analog input will be converted.
The analog input can fall outside that window, but it won't be converted.
If the analog input falls outside the range -0.3V to 4.3V it will harm the device.

 

[keith1200rs]

Ok so its basically saying you have a 1V window around Vref in which the analog input will be converted.
The analog input can fall outside that window, but it won't be converted.
If the analog input falls outside the range -0.3V to 4.3V it will harm the device.

If the analog input is outside the conversion window you will get either max or min value but otherwise, yes, you are correct.

Keith

 

[FvM]

If the analog input falls outside the range -0.3V to 4.3V it will harm the device.

Some manufacturers specify a maximum input current that can be accepted by the clamp diodes, e.g. +/- 10 mA.